Sealed container for electrode assemblies



NV T1,, 194% L. J. LA BREE 2,486,482

SEALED CONTAINER FOR ELECTRODE ASSEMBLIES Filed Oct. 18, 1945 2 Sheets-Sheet 2 l/V VISA/TOR 5V LJ. M: if

Patented Nov. 1 1949 SEALED CONTAINER FOR ELECTRODE ASSEMBLIES Laurent: J. La Brie, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 18, 1945, Serial No. 623,150

12 Claims. 1

This invention relates to a sealed casing for anelectrode assembly and more particularly to such casings for enclosing piezoelectric crystal mountings.

Piezoelectric quartz crystals are employed in various-types of oscillator equipment to resonate at a desired frequency and are usually enclosed in a casing to avoid injury to the crystal. However, in addition to mechanical injury the crystal frequency limits are also affected by moisture and other deleterious foreign substances which may enter the casing and greatly alter the resonance characteristics of the crystal.

The main object of this invention is to protect the crystal in a hermetically sealed casing of compact construction.

Another object of the invention is to facilitate the assembly of the casing and crystal mounting to eliminate the entrance of moisture in the casing.

A further object of the invention is to enclose the crystal in a sealed casing of minimum dimensions so that the assembly may be incorporated in congested surroundings and thereby reduce mounting requirements in equipment.

Another object of the invention is to reduce assembly time and cost in the fabrication of the crystal unit.

These objects are attained in accordance with this invention by an assembly casing involving a barrel or shell and a pair of end closure caps secured to the shell in hermetically sealed relation, the caps having terminal conductors insulatingly extending therethrough and provided with contacts for supporting the crystal mounting. In one aspect of the invention the caps are provided with axial conductors extending through glass seals with contact portions in pressure engagement with a sandwich mounting assembly of the crystal. A cylindrical metallic shell surrounds the crystal mounting which is centrally supported therein and the caps are sealed over the ends of the shell to hermetically close the casing against the entrance of moisture. In another form the ends of the shell are compressed over the caps with an interposed rubber compound between the contacting boundaries to produce an air-tight seal or joint to eliminate moisture. In a further embodiment, auxiliary wedge rings are incorporated in the caps and the coated ends of the shell are deformed between the rings and the caps to form the seals. This construction insures a compact and efficiently sealed casing which can be fabricated at low cost, is compatible to mass production and fulfils the prerequisites for maintaining a constant dry environment within the casing so that the crystal frequency is unalterable.

The various features enumerated above and others are set forth with more particulars in the following detailed description and are shown in the accompanying drawings.

Fig. 1 is an enlarged view in elevation, partly in section, showing one form of the invention in which the caps are sealed over the shell portion of the casing;

Fig. 2 illustrates another form of the invention, partly in section, to show the modification of the seal between the caps and the shell;

Fig. 3 shows another modification of the invention with the casing broken away in which auxiliary deforming rings are incorporated in the casing to insure a'tight joint at the sealing edges of the casing;

Fig. 4 is a perspective exploded view of the form of the invention shown in Fig. 3 showing the detailed elements entering into the assembly of the crystal unit;

Fig. 5 is a partial view in cross-section of the casing 'prior to the final compression and closure operations for completing the sealing of the unit; and

Fig. 6 is another view in section of the assembly showing a modification in which the crystal mounting is supported by spring pressure contacts on both conductors.

Referring to the drawing and particularly to Fig. l, the sealed casing of this invention is shown on a scale about four timesgreater than the actual unit which has a diameter and length of the main casing of /,--inch and an over-all length between the conductors of slightly more than 1 inch. The sealed casing of this invention includes a cylindrical metallic shell or body member ID, preferably of a metal such as halfhard brass, having a uniform diameter and wall thickness and constituting an enclosure or housing for a crystal mounting in which the crystal of the flanges.

trally supported in the barrel casing under com pression by a rigid cup-shaped contact member l4, preferably of beryllium copper plated with tin, attached to the inner end of a terminal conductor l5 and a bifurcated spring contact 45, of phosphor bronze, engages the opposing mounting plate of the crystal assembly and is attached to a central conductor I1 extending outwardly from the opposite end of the casing. The casing is terminated by a pair of oppositely disposed annular metallic caps or closure members l8 and is having a neck portion 20 extending outwardly from the casing and coaxially surrounding the conductor, and a flange portion 2| surrounding the body or shell 10 of the casing. The metallic caps and the conductors are preferably formed of a nickel-iron-cobalt alloy, such as Kovar," to facilitate the production of a hermetic sealed joint with the conductors in the cavity of the neck portion with a vitreous material, such as borosilicate glass, which readily wets the metal surfaces of the cap and the conductor to form a vacuum-tight joint therewith, the glass and the metal having about the same coefitcient of expansion and therefore maintains an efflcient seal for the conductors. The vitreous seal, in the form of a disc stopper or plug 22, fills the neck portion of the cap and has parallel surfaces coincident with the extremities of the neck portion of the cap so that the glass seal extends no further than the termination of the neck portion and therefore tends to reduce the over-all length of the assembly. The fiange portions 2| of the cap are sealed over the telescoped ends of the barrel portion In 'by a filling of solder 23 to form an air-tight joint around the boundaries between the caps and the barrel to prevent the entrance of moisture into the casing. The projecting ends of the conductors are also provided with contact sleeves 24 of a non-oxidizing metal, such as a silver-copper alloy. This construction forms a compact symmetrical housing or receptacle for the mounting of the crystal assembly which efficiently protects the crystal mounting against changes in frequency of the crystal due to the entrance of moisture or deleterious atmospheric matter and provides a unit of small size which can be fabricated by mass production methods at low cost.

Referring to Fig. 2 the invention is modified to provide a different type of seal at the extremities of the cap members l8 and [9 wherein the exterior surfaces of the cap members, namely,

the flanges 2|, are coated with a plastic layer 25,

such as a synthetic rubber substance, preferably neoprene cement, which is applied in the form of a coating or may be prefabricated in the form of a gasket and applied to the exterior surface In this form of the invention the barrel or shell portion of the casing has an intermediate thick wall portion 26 having an internal diameter slightly larger than the diameter of the crystal and mounting plates and oppositely extending thin wall portions 21 which extend exterior to and beyond the ends of the flanges 2| of the caps, the caps abutting against the shoulders of the thick wall portion to space them in relation to the casing and the interposed crystal mounting. The thin wall portions of the barrel portion or shell are spun over the shoulder portions of the caps to compress the plastic cement layer 25 on the surfaces of the caps and thereby provide a hermetic seal to maintain the environment within the casing in a constant dry 4 state. In this construction the deformable plastic sealing material efficiently seals all Joints between the contacting surfaces of the caps and the thin wall portions of the casing to provide a tight joint which eliminates the entrance of moisture.

Another modification of the invention is shown in Fig. 3 in which the annular seals of the casing are produced in a different manner than as shown in Fig. 2. In this arrangement the thin walls 28 of the terminating ends of the barrel or shell portion of the casing are of uniform diameter and extend outwardly from a thickened wall portion 29 of the casing having the same internal diameter as the end walls but the thick wall portion 29 is provided with external annular shoulder portions 30 to form limit abutments for the end caps I8 and IS. The thin wall portions 28 of the shell are coated externally with the neoprene cement, which may be mixed with benzene to reduce the consistency, and applied in a thin film over the wall portions 28 and the right angle surfaces of the shoulders 30. In order to insure a tight seal around the periphery of the shell and the end cap members a pair of rigid wedge rings 3| and 32, preferably of hard brass, are mounted within the end cap members and adjacent to the flange portions 2| thereof. The wedge rings, as shown more clearly in Fig. 4, have a uniform internal diameter slightly less than the diameter of the shell and an increasing diameter on the external surfaces from both edges to form a mid-point ridge 33 of greatest diameter and slightly less than the internal diameter of the end cap members l8 and I9.

In the preliminary assembly of the unit the wedge rings are seated within their respective caps l8 and IS, the barrel being placed in one of the caps and the crystal mounting involving the crystal disc II and the mounting blocks [2,

and I3 inserted in the barrel and the opposite end cap with the wedge ring therein placed on the opposite edge of the :barrel. In this assembly, as shown more clearly in Fig. 5, the thin wall portion 28 of the barrel or shell fits loosely in the cavity between the conjoint surfaces of the flange portion of the cap and the outer tapered surface of the wedge ring where the shell is temporarily seated in the end cap members. The loose assembly is then placed in a jig and inserted in an oven to thoroughly dry the elements entering into the assembly of the casing and to vaporize the solvent in the cement coating applied to the shell. When the air in the casing is thoroughly dry the end caps are compressed toward the shoulder portions 30 of the shell, to force the thin end walls of the shell into the end caps and apply the desired pressure on the conductors to centrally support the crystal mounting in the casing. Finally, the fiange portions 2| of the end cap members are shrunk inwardly, preferably by clinching or crimping so that the thin end wall portions 28 are deformed over the wedge rings and the plastic rubber-like cement fiows into the crevices between the cap flanges and the wedge rings, to form air-tight seals around the periphery of the shell.

Fig. 6 shows another modification of the assembly in which the crystal mounting is supported under spring pressure from opposite sides by the substitution of a second bifurcated spring disc contact 34 attached to conductor [5 instead of the rigid cup contact H, as shown in the other fi ures.

While the invention has been disclosed in various aspects to illustrate various sealed joints for the hermetically sealed casing of this invention, it is of course understood that various modifications may be made therein to achieve the results of this invention and while the disclosure relates particularly to the mounting of a crystal assembly in the hermetic casing it is, of course, understood that other electrode assemblies or electrical apparatus may be mounted in the casing in accordance with this invention without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A sealed casing for an electrode assembly comprising a hollow metallic body portion, apertured metallic cap members on opposite ends of said body portion, a pair of axial conductors extending through said cap members, contacts carried by said conductors within said body portion for engagement with said electrode assembly, to hold said assembly under compression, vitreous closures sealing said conductors in said apertured cap members, and a sealing coating material interposed between the contacting surfaces of said body portion and cap members for hermetically sealing said casing against the entrance of mois ture.

2. A sealed casing for an electrode assembly comprising a hollow metallic body portion, 'apertured metallic cap members on opposite ends of said body portion, a pair of axial conductors extending through said cap members, a rigid contact carried by one of said conductors, a resilient contact on the opposing conductor and spaced in axial relation to said rigid contact, said contact being in pressure engagement with said electrode assembly, vitreous closures sealing said conductors in said apertured cap members, and a sealing coating material interposed between the contacting surfaces of said body portion and cap members for hermetically sealing said casing against the entrance of moisture.

3. A sealed casing for an electrode assembly comprising a hollow metallic body portion, apertured metallic cap members on opposite ends of said body portion, a pair of axial conductors extending through said cap members, a rigid cup shaped contact extending within said body portion and supported on one of said conductors, a bifurcated spring disc contact supported on the other conductor in opposed axial relation with said body portion, said contact being in pressure engagement with said electrode assembly, vitreous closures sealing said conductors in said apertured cap members, and a sealing coating material interposed between the contacting surfaces of said body portion and cap members for hermetically sealing said casing against the entrance of moisture.

4. A sealed casing for an electrode assembly comprising a hollow metallic body member having deformable end portions, apertured metallic cap elements adjacent said end portions, conductors extending through said cap element in axial alignment, a vitreous sealing mass surrounding each conductor and filling the opening in each of said cap elements, said conductors being in pressure engagement with the electrode assembly centrally mounted within said body member, and a plastic sealing layer interposed between said cap element and said deformable end portion of said body member.

5. A sealed casing for an electrode assembly tors extending through said cap element in axial alignment, a vitreous sealing mass surrounding each conductor and filling the opening in each cap element, said conductors being in pressure engagement with the electrode assembly centrally mounted within said body member, and a plastic sealing layer engaging the periphery of said cap element, said deformable end portions compressing said layer on said cap element to form a tight sealed joint.

6. A sealed casing for an electrode assembly comprising a hollow metallic body member having deformable end portions, apertured metallic cap elements adjacent said end portions, conductors extending through said cap elements in axial alignment, a vitreous sealing mass surrounding each conductor and filling the opening in each cap element, said conductors being in pressure engagement with the electrode assembly centrally mounted within said body member, and a plastic sealing layer engaging the periphery of said end portions, said cap elements embracing said end portions to compressibly seal said casing by presure contact with said sealing layer.

7. A sealed unit for an electrode assembly comprising a hollow metallic body member havin the outer end surfaces coated with sealing material, metallic cap elements closing the ends of said body member, conductors extending through said cap elements in axial alignment, a vitreous mass supporting each conductor in each cap element, metallic contacts carried by said conductors within said body member, an electrode assembly disposed within said body member, said contacts being in pressure engagement with said electrode assembly from opposite sides, and said cap elements having rim portions clamped around the opposite end peripheries of said body member to compress said sealing material therebetween and form an air-tight joint.

8. A sealed casing for a crystal mounting comprising a cylindrical metallic casing having reduced end portions, a plastic coating on the exterior surface of said end portions, wedge rings within said casing engaging the inner surfaces of said end portions, conductors extending into said casing from opposite ends and in coaxial relation thereto, said conductors having contacts in pressure engagement with the crystal mounting held centrally in said casing, annular metallic closures compressing said end portions and coating against said rings, and vitreous sealing masses hermetically in contact with said closures and said conductors.

9. A sealed casing for a crystal mounting comprising a cylindrical metallic casing having reduced end portions, a rubber-like cement applied to said end portions, a pair of annular metallic closures embracing said end portions to compress said cement and form an air-tight joint, conductors extending through said closures having contacts in pressure engagement with a central crystal mounting, and hermetic vitreous seals carried by said closures and surrounding said conductors.

10. A sealed casing for a crystal mounting comprising a cylindrical metallic casing having reduced end portions, a rubber-like cement applied to said end portions, a pair of annular metallic closures embracing said end portions to compress said cement and form an airtight joint, conductors extending through said closures having contacts in pressure engagement with a central crystal mounting, hermetic vitreous seals carried by said closures and surrounding said conductors, and internal metallic rings located in juxtaposed relation to said end portions and counteracting the pressure produced by said closures.

11. The method of hermetically sealing an electrode mounting casing having a metallic barrel body and end cap portions with central conduc- 8 tors sealed therein which comprises coating the end portions of said body with a plastic cement, fitting wedge rings within said cap portions, inserting a crystal mounting in said body between said conductors, adjusting the ends of said barrel body between said cap portions and wedge rings, pressing said cap portions and rings in, telescopic relation around said body ends, and shrinking said cap portions to induce said body ends to conform to the shape oi said wedge rings and cause said cement to flow to seal the boundaries of said caps against entrance of moisture.

LAURENTS J. LA BRIE.

REFERENCES CITED UNITED STATES PATENTS Name Date Dennick et a1 June 11, 1946 Number 

